1. Field of the Invention
The present invention relates generally to a head drum for a video cassette recorder (VCR) and its fabrication method and, more particularly, to a VCR head drum which has increased abrasion resistance and lubricity and also prevents video tape damage.
2. Description of the Related Art
As the mechanism of a VCR becomes more compact and complex, the thickness of the air gap which minimizes the friction between the VCR tape and the head drum tends to decrease, which in turn increases the likelihood of contact between the tape and the drum. This tendency became more distinct as home use VCR's have gradually adopted jog shuttle function. Accordingly, the mutual abrasion between the tape and the head drum has become a critical factor to the lifetime of a VCR. To minimize the size of a VCR, it must be possible to play the tape in a stable condition with a small driving force. To this end, it is necessary to minimize the friction between the tape and each part of the VCR.
According to a recent specification on the digital VCR or HDTV VCR published in Nikke Electronics Asia (September, 1993) p.40, the required information storage and playback speed of the VCR will be twice that of the conventional ones. Such a high speed information processing necessarily requires increased revolution speed of the head drum. Therefore, the revolution speed of the next generation VCR is expected to reach up to 9000 rpm. At this speed, the friction between the head drum and the VCR tape emerges as an even more serious problem.
Accordingly, there has been many attepmts to overcome this ploblem. According to an article published in The Journal of the Korean Institute of Metal and Materials, 6 (4), 1993 by K. R. Lee and K. Y. Eun, a diamond-like hard carbon film exhibits superior mechanical characteristics, acid resistance, and lubricity. The application of the diamond-like hard carbon film is being studied extensively, which includes the protective coating of magnetic recording media (computer hard disk, etc.), the lubricative coating of micro-mechanisms, coatings for various cutting tools like a razer blade, protective coating for an optical fiber, and coating for biomedical materials such as artificial joints, etc. A research for improving the performance and durability of VCR's by coating a diamond-like hard carbon film on the side surface of the head drum which makes contact with the VCR tape was reported by H. Nakaue in Thin Solid Films, Vol.212 (1992) p.240.
An operation test was performed for a VCR mounting such a head drum coated with a diamond-like hard carbon film. The test result showed that the VCR tape was damaged, and the magnetic powder separated from the tape and its mixture with the binding material contaminated the surface of the head drum badly. Moreover, the seperated magnetic powder in turn causes severe damage to the surface of the head because of its high degree of hardness.
This problem occurs because the tape is damaged by the defective portions on the coated drum surface or by the edges of the drum owing to the sharply increased hardness of the coated drum surface. Thus, this problem remains to be solved before the diamond-like hard carbon film can be used as a solution to the increased friction between the head drum and the tape resulting from the higher revolution rate of the head drum.
Therefore, a need exists in the art for a method for improving the durability and abrasion resistance of a head drum without causing the aforementioned problems of causing damage to the VCR tape and contaminating the drum surface. The present invention fulfills this need, and further provides related advantages.